Wireless network hybrid positioning

ABSTRACT

Methods and apparatuses for position determination and other operations. In one embodiment of the present invention, a mobile station uses wireless signals from a plurality of wireless networks (e.g., with different air interfaces and/or operated by different service providers) for position determination (e.g., for data communication, for obtaining time and/or frequency information, for range measurement, for sector or altitude estimation). In one embodiment of the present invention, mobile stations are used to harvest statistical data about wireless access points (e.g., the locations of mobile stations that have received signals from the wireless access points, such as from cellular base stations, wireless local area network access points, repeaters for positioning signals or other wireless communication transmitters) and to derive location information (e.g., position and coverage area of the wireless access points) for the wireless networks from the collected statistical data.

This application claims priority to and is a divisional of U.S. patentapplication Ser. No. 13/354,235, filed Jan. 19, 2012, which claimspriority to and is a continuation of U.S. patent application Ser. No.10/877,205, filed Jun. 25, 2004, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/483,094, filed Jun. 27, 2003,each of which is expressly incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to position determination systems, and moreparticularly, to hybrid positioning using wireless communicationsignals.

BACKGROUND

To perform position location in wireless cellular networks (e.g., acellular telephone network), several approaches perform trilaterationbased upon the use of timing information sent between each of severalbase stations and a mobile device, such as a cellular telephone. Oneapproach, called Advanced Forward Link Trilateration (AFLT) in CDMA orEnhanced Observed Time Difference (EOTD) in GSM or Observed TimeDifference of Arrival (OTDOA) in WCDMA, measures at the mobile devicethe relative times of arrival of signals transmitted from each ofseveral base stations. These times are transmitted to a Location Server(e.g., a Position Determination Entity (PDE) in CDMA), which computesthe position of the mobile device using these times of reception. Thetransmit times at these base stations are coordinated such that at aparticular instance of time, the times-of-day associated with multiplebase stations are within a specified error bound. The accurate positionsof the base stations and the times of reception are used to determinethe position of the mobile device.

FIG. 1 shows an example of an AFLT system where the times of reception(TR1, TR2 and TR3) of signals from cellular base stations 101, 103 and105 are measured at the mobile cellular telephone 111. This timing datamay then be used to compute the position of the mobile device. Suchcomputation may be done at the mobile device itself or at a locationserver if the timing information so obtained by the mobile device istransmitted to the location server via a communication link. Typically,the times of receptions are communicated to a location server 115through one of the cellular base stations (e.g., base station 101, 103or 105). The location server 115 is coupled to receive data from thebase stations through the mobile switching center 113. The locationserver 115 may include a base station almanac (BSA) server, whichprovides the location of the base stations and/or the coverage area ofbase stations. Alternatively, the location server 115 and the BSA servermay be separate from each other; and the location server 115communicates with the base station to obtain the base station almanacfor position determination. The mobile switching center 113 providessignals (e.g., voice communications) to and from the land-line PublicSwitched Telephone Network (PSTN) 117 so that signals may be conveyed toand from the mobile telephone to other telephones (e.g., land-linephones on the PSTN 117 or other mobile telephones). In some cases thelocation server 115 may also communicate with the mobile switchingcenter 113 via a cellular link. The location server 115 may also monitoremissions from several of the base stations 101, 103, 105 in an effortto determine the relative timing of these emissions.

In another approach, called Uplink Time of Arrival (UTOA), the times ofreception of a signal from a mobile device is measured at several basestations (e.g., measurements taken at base stations 101, 103 and 105).FIG. 1 applies to this case if the arrows of TR1, TR2 and TR3 arereversed. This timing data may then be communicated to the locationserver 115 to compute the position of the mobile device.

Yet a third method of doing position location involves the use in themobile device of circuitry for the United States Global PositioningSatellite (GPS) system or other Satellite Positioning Systems (SPS),such as the Russian GLONASS system and the proposed European GalileoSystem or a combination of satellites and pseudolites. Pseudolites areground-based transmitters, which broadcast a PN code (similar to a GPSsignal) modulated on an L-band carrier signal, generally synchronizedwith SPS time. Each transmitter may be assigned a unique PN code so asto permit identification by a mobile device. Pseudolites are useful insituations where SPS signals from an orbiting satellite might beunavailable, such as tunnels, mines, buildings or other enclosed areas.The term “satellite”, as used herein, is intended to include pseudo liteor equivalents of pseudolites, and the term GPS signals, as used herein,is intended to include GPS-like signals from pseudolites or equivalentsof pseudolites. Methods that use an SPS receiver to determine a positionof a mobile station may be completely autonomous (in which the SPSreceiver, without any assistance, determines the position of the mobilestation) or may utilize the wireless network to provide assistance dataor to share in the position calculation. Examples of such methods aredescribed in U.S. Pat. Nos. 5,812,087; 5,841,396; 5,874,914; 5,945,944and 6,208,290. For instance, these patents describe, among other things:a method to obtain from cellular phone transmission signals accuratetime information, which is used in combination with SPS signals todetermine the position of the receiver; a method to transmit the Dopplerfrequency shifts of in-view satellites to the receiver on the mobiledevice through a communication link to determine the position of themobile device; a method to transmit satellite almanac data (or ephemerisdata) to a receiver through a communication link to help the receiver todetermine its position; a method to lock to a precision carrierfrequency signal of a cellular telephone system to provide a referencesignal at the receiver for SPS signal acquisition; a method to use anapproximate location of a receiver to determine an approximate Dopplerfor reducing SPS signal processing time; and a method to comparedifferent records of a satellite data message received to determine atime at which one of the records is received at a receiver in order todetermine the position of the receiver. In practical low-costimplementations, both the mobile cellular communications receiver andthe SPS receiver are integrated into the same enclosure and may in factshare common electronic circuitry.

In yet another variation of the above methods, the round trip delay(RTD) is found for signals that are sent from the base station to themobile device and then are returned. In a similar, but alternative,method the round trip delay is found for signals that are sent from themobile device to the base station and then returned. Each of theseround-trip delays is divided by two to determine an estimate of theone-way propagation delay. Knowledge of the location of the basestation, plus a one-way delay constrains the location of the mobiledevice to a circle on the earth. Two such measurements from distinctbase stations then result in the intersection of two circles, which inturn constrains the location to two points on the earth. A thirdmeasurement (even an angle of arrival or cell sector identification)resolves the ambiguity.

A combination of either the AFLT or U-TDOA with an SPS system may bereferred to as a “hybrid” system. For example, U.S. Pat. No. 5,999,124describes, among other things, a hybrid system, in which the position ofa cell based transceiver is determined from a combination of at least:i) a time measurement that represents a time of travel of a message inthe cell based communication signals between the cell based transceiverand a communication system; and ii) a time measurement that represents atime of travel of an SPS signal.

Altitude aiding has been used in various methods for determining theposition of a mobile device. Altitude aiding is typically based on apseudo-measurement of the altitude. The knowledge of the altitude of alocation of a mobile device constrains the possible positions of themobile device to a surface of a sphere (or an ellipsoid) with its centerlocated at the center of the earth. This knowledge may be used to reducethe number of independent measurements required to determine theposition of the mobile device. For example, U.S. Pat. No. 6,061,018describes, among other things, a method where an estimated altitude isdetermined from the information of a cell object, which may be a cellsite that has a cell site transmitter in communication with the mobiledevice.

SUMMARY OF THE DESCRIPTION

In one aspect of the present invention, a method of determining aposition of a mobile station, the method comprising: receiving wirelesssignals from a first wireless network; receiving wireless signals from asecond wireless network; determining timing measurements based on thewireless signals from the first wireless network and the wirelesssignals from the second wireless network; and determining the positionof the mobile station based on the timing measurements.

In another aspect of the present invention, a method of determining aposition of a mobile station, the method comprising: receiving wirelesssignals from a first base station in a first wireless network, whereinthe mobile station is unauthorized for access to the first wirelessnetwork; receiving wireless signals from a second base station in asecond wireless network, wherein the mobile station is subscribed to thesecond wireless network; determining a first identity of the first basestation in the first wireless network; determining a second identity ofthe second base station in the second wireless network; transmitting thefirst and second base station identities to a location server havingaccess to a base station almanac; retrieving corresponding positions ofthe first and second base stations based on the first and second basestation identities; and determining the position of the mobile stationbased on the timing measurements.

In another aspect of the present invention, a mobile device fordetermining a position of the mobile station, the mobile devicecomprising: means for receiving wireless signals from a first wirelessnetwork; means for receiving wireless signals from a second wirelessnetwork; means for determining timing measurements based on the wirelesssignals from the first wireless network and the wireless signals fromthe second wireless network; and means for determining the position ofthe mobile station based on the timing measurements.

In another aspect of the present invention, a mobile device comprising aprocessor and a memory wherein the memory includes software instructionsto: receive wireless signals from a first wireless network; receivewireless signals from a second wireless network; determine timingmeasurements based on the wireless signals from the first wirelessnetwork and the wireless signals from the second wireless network; anddetermine the position of the mobile station based on the timingmeasurements.

In another aspect of the present invention, a non-transitory computerreadable medium tangibly embodying a program of machine-readableinstructions executable by a digital processing apparatus to perform amethod for determining a position of a mobile station having memory anda processor, said method comprising operations of: receiving wirelesssignals from a first wireless network; receiving wireless signals from asecond wireless network; determining timing measurements based on thewireless signals from the first wireless network and the wirelesssignals from the second wireless network; and determining the positionof the mobile station based on the timing measurements.

The present invention includes methods and apparatuses that performthese methods, including data processing systems, which perform thesemethods, and computer readable media that when executed on dataprocessing systems cause the systems to perform these methods. Further,the inventions described herein may be implemented on different nodeswithin a system, such nodes including a mobile station, a base station(such as a wireless access point) or a location server or other nodes ina network or wireless network.

Other features of the present invention will be apparent from theaccompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 shows an example of a prior art cellular network, whichdetermines the position of a mobile cellular device.

FIG. 2 shows an example of a server, which may be used with the presentinvention.

FIG. 3 shows a block diagram representation of a mobile stationaccording to one embodiment of the present invention.

FIG. 4 shows one example of a hybrid positioning system according to oneembodiment of the present invention.

FIG. 5 shows another example of a hybrid positioning system according toone embodiment of the present invention.

FIG. 6 illustrates one method to determine the position of a wirelessaccess point according to one embodiment of the present invention.

FIG. 7 illustrates another method to determine the position informationof a wireless access point according to one embodiment of the presentinvention.

FIG. 8 shows a method of hybrid position determination using a pluralityof wireless networks according to one embodiment of the presentinvention.

FIG. 9 shows a method of hybrid position determination using twowireless networks for communication with a server according to oneembodiment of the present invention.

FIG. 10 shows a method to generate location information about a wirelessaccess point according to one embodiment of the present invention.

FIG. 11 shows a hybrid position determination method using one wirelessnetwork for communication and another wireless network for themeasurement of positioning parameters according to one embodiment of thepresent invention.

FIG. 12 shows flowchart of a hybrid positioning system according to oneembodiment of the present invention.

FIG. 13 shows another flowchart of a hybrid positioning system accordingto one embodiment of the present invention.

FIG. 14 shows a flowchart of a method to determine the positioninformation of a wireless access point according to one embodiment ofthe present invention.

DETAILED DESCRIPTION

The following description and drawings are illustrative of the inventionand are not to be construed as limiting the invention. Numerous specificdetails are described to provide a thorough understanding of the presentinvention. However, in certain instances, well known or conventionaldetails are not described in order to avoid obscuring the description ofthe present invention. References to one or an embodiment in the presentdisclosure are not necessary to the same embodiment; and such referencesmean at least one.

Recent development of wireless communication technologies leads to thedeployment of various different wireless networks with substantialoverlapping coverage in some areas. In the present application, awireless network refers to a set of wireless access points (e.g., basestations) with a same air interface, operated by one service provider(e.g., Verizon Wireless or Sprint), such that a mobile unit can accessthe network through one of the set of the wireless access points when inthe coverage area of the network; and the union of the coverage areas ofthe wireless access points of the wireless network is the coverage areaof the network. Further, data communication refers to the transmissionof data in a two-way communication system although, in certainembodiments, data communication may be a one-way communication or mayinclude extracting information embedded in a signal, which isbroadcasted regardless whether the receiver needs it or not. A wirelessaccess point may be considered to be a cell tower or a base station orother wireless transmitter or receiver, which is coupled to a network ofother nodes (for example, the wireless access point is coupled bywireless or wire line to the other nodes).

In certain areas, especially urban metropolitan areas, differentwireless networks have substantially overlapping coverage. For example,different service providers may offer the same type of wireless service(e.g., cellular phone communication) in the same area. Further,different types of wireless services, such as wireless phone services(e.g., cellular phone services for data, voice or both) and wirelessdigital communication services (e.g., wireless local area networks suchas WiFi networks, bluetooth, ultra-wideband), may have overlapping incoverage area. For example, wireless LAN (Local Area Network) accesspoints (e.g., for an IEEE 802.11 based wireless network) may be locatedwithin the coverage areas of wireless telecommunication networks (e.g.,based on Telecommunications Industry Association (TIA)/ElectronicIndustries Alliance (EIA) Standards, such as IS-95, IS-856 or IS-2000),such as those based on TDMA (Time Division Multiple Access), GSM (GlobalSystem for Mobile communications), CDMA (Code Division Multiple Access),WCDMA (Wideband Code Division Multiple Access), UMTS (Universal MobileTelecommunication System), TD-SCDMA (Time Division Synchronous CodeDivision Multiple Access), iDEN (integrated Digital Enhanced Network),HDR (High Data Rate) or other similar cellular networks.

At least one embodiment of the present invention seeks a comprehensivesystem, which supports positioning using these disparate sources ofwireless signals to determine measurements and to obtain aidinginformation (e.g., the position and the coverage area of an accesspoint, Doppler frequency shifts for in-view SPS satellites, SPSephemeris data) to form a flexible and ubiquitous navigation solution.In this comprehensive system, when information about an access point(e.g., base station almanac, such as the location and coverage area ofthe base station) is available, it is used and may be enhanced. Where itis not, the system may automatically gather and enhance such informationfor the benefit of future positioning attempts.

At least one embodiment of the present invention uses wireless signalstransmitted from access points of more than one wireless network tocombine information, such as SPS observations, wireless networkobservations, terrain elevation information and others, to obtain aposition solution for a mobile station. In one embodiment of the presentinvention, a mobile station of a hybrid position system transfersinformation over access points of more than one wireless network (intwo-way communication) to aid in the acquisition of SPS signals, timestamping for measurements and other operations at the mobile station. Inone embodiment of the present invention, a mobile station of a hybridposition system performs measurements using signals from access pointsof different wireless networks, while communicating with a remote serverusing one or more of the wireless networks.

Typically, information describing the identification, location andcoverage area of the sectors of a wireless network is stored in a basestation almanac, which has been used in a hybrid positioning systemusing a single wireless network. However, when different wirelessnetworks (e.g., different service providers or different types ofnetworks) have overlapping coverage, a typical mobile station does nothave access to such information for the access points of the differentwireless networks, even though the wireless signals transmitted from theaccess points of the different wireless networks are in the air andavailable to the mobile station. This is usually because the mobilestation is allowed or is authorized to have access to one wirelessnetwork but not another wireless network. One simple example of this isa cell phone that has been authorized access to a first wireless network(e.g., a cell phone network operated by a service provider such asVerizon Wireless) but has not been authorized access to a secondwireless network (e.g., Sprint's cell phone network) or to a thirdwireless network (e.g., a Wi-Fi “hotspot”).

In one embodiment of the present invention, when available, informationfrom small and localized transmitters, such as an IEEE 802.11 wirelessLAN access point, is incorporated into the wireless navigation solution.In many cases, the location information for these transmitters is notwell known. In some cases, the “almanac” information describing thephysical characteristics of a wireless network (e.g., ID, location andcoverage area of access points) is not available to users who might liketo use it. Some network providers may choose not to share suchinformation, while still others may not have it available. In oneembodiment of the present invention, information for deriving thephysical characteristics of a network is gathered from mobile stationsthat use another wireless network for communication. In one embodimentof the present invention, using the wireless signals available in theair from different wireless networks and the abilities of the mobilestation for position determination (e.g., a cell phone with a GPSreceiver or with a portion of a GPS receiver), mobile stations harvestinformation about the access points of the different wireless networks,which in general may not be under control of an operator of a wirelessnetwork through which the mobile stations typically perform datacommunication. The harvested information is used to derive locationinformation (e.g., the location, coverage area) about the access points,which can be used for aiding hybrid position determination for futureposition determinations.

In one embodiment of the present invention, the signals used to providetime information and/or frequency information to a mobile station arenot the same as the one over which data communication transactions arecarried out.

A mobile station that supports multiple wireless communicationinterfaces (e.g., IEEE 802.11 [and other IEEE 802 standards such as802.15, 802.16 and 802.20], Bluetooth, UWB [Ultra-Wideband], TDMA, GSM,CDMA, W-CDMA, UMTS, TD-SCDMA, iDEN, HDR or other similar networks) isused in one embodiment of the present invention to use multiple wirelessnetworks. Such a mobile station may have, for example, several differentportions in a communication section, which support the transmissionand/or reception of data for these different communication interfaces.Thus, one portion may handle the transmission and/or reception of Wi-Fisignals (e.g., IEEE 802.11 or 802.16) and another portion of thecommunication section may support a cellular telephone interface such asa CDMA interface. This also gives the user alternative communicationpaths from which to choose when deciding to communicate. For example,the availability, coverage, expense, data speed and ease of use may beconsidered when choosing which communication path to use.

In one embodiment of the present invention, a first wireless network isused for communications and positioning, while a second wireless networkis used for positioning and optionally communications. For example, eachof these wireless networks might use a completely different airinterface (e.g., different TIA/EIA standards), such as an air interfacethat is for a typical wireless cell phone (e.g., TDMA, GSM, CDMA,W-CDMA, UMTS, TD-SCDMA, iDEN, HDR or other similar cellular networks) orsome other wireless air interface, such as that in accordance with IEEE802.11, bluetooth or UWB. A plurality of these wireless networks is usedfor positioning purposes, even when only one wireless network may beused for communications. The advantages of a hybrid approach accordingto at least some of the embodiments of the present invention include:improved redundancy for a more failsafe solution, higher positioningavailability, better accuracy and faster time to fix.

FIG. 2 shows an example of a data processing system, which may be usedas a server in various embodiments of the present invention. Forexample, as described in U.S. Pat. No. 5,841,396, the server 201 mayprovide assistance data such as Doppler or other satellite assistancedata to the GPS receiver in a mobile station. In addition oralternatively, the same server or a different server may perform thefinal position calculation rather than the mobile station (afterreceiving pseudoranges or other data from which pseudoranges can bedetermined from the mobile station) and then may forward this positiondetermination result to the base station or to some other system. Thedata processing system as a server (e.g., a location server, an almanacserver) typically includes communication devices 212, such as modems ornetwork interface. The location server may be coupled to a number ofdifferent networks 220 through communication devices 212 (e.g., modemsor other network interfaces). Such networks include one or moreintranets, the network, the cellular switching center or multiplecellular switching centers 225, the land based phone system switches223, cellular base stations (not shown in FIG. 2), GPS receivers 227 orother processors or location servers 221.

Multiple cellular base stations are typically arranged to cover ageographical area with radio coverage. These different base stations arecoupled to at least one mobile switching center, as is well known in theprior art (e.g., see FIG. 1). Thus, multiple base stations would begeographically distributed but coupled together by a mobile switchingcenter. The network 220 may be connected to a network of reference GPSreceivers 227 that provide differential GPS information and may alsoprovide GPS ephemeris data for use in calculating the position of mobilestations. The network 220 is coupled through the modem or othercommunication interface to the processor 203. The network 220 may beconnected to other computers or network components. Also network 220 maybe connected to computer systems operated by emergency operators, suchas the Public Safety Answering Points, which respond to 911 telephonecalls. Various examples of methods for using a location server have beendescribed in numerous U.S. patents, including: U.S. Pat. Nos. 5,841,396,5,874,914, 5,812,087 and 6,215,442.

The server 201, which is a form of a data processing system, includes abus 202 which is coupled to a microprocessor 203 and a ROM 207 andvolatile RAM 205 and a non-volatile memory 206. The processor 203 iscoupled to cache memory 204 as shown in the example of FIG. 2. The bus202 interconnects these various components together. While FIG. 2 showsthat the non-volatile memory 206 is a local device coupled directly tothe rest of the components in the data processing system, it will beappreciated that the present invention may utilize a non-volatile memorythat is remote from the system, such as a network storage device, whichis coupled to the data processing system through a network interfacesuch as a modem or Ethernet interface. The bus 202 may include one ormore buses connected to each other through various bridges, controllersand/or adapters as is well known in the art. In many situations thelocation server may perform its operations automatically without humanassistance. In some designs where human interaction is required, the I/Ocontroller 209 may communicate with displays, keyboards and other I/Odevices.

Note that while FIG. 2 illustrates various components of a dataprocessing system, it is not intended to represent any particulararchitecture or manner of interconnecting the components as such detailsare not germane to the present invention. It will also be appreciatedthat network computers and other data processing systems that have fewercomponents or perhaps more components may also be used with the presentinvention and may act as a location server or a PDE (positiondetermination entity).

In some embodiments, the methods of the present invention may beperformed on computer systems that are simultaneously used for otherfunctions, such as cellular switching, messaging services, etc. In thesecases, some or all of the hardware of FIG. 2 would be shared for severalfunctions.

It will be apparent from this description that aspects of the presentinvention may be embodied, at least in part, in software. That is, thetechniques may be carried out in a computer system or other dataprocessing system in response to its processor executing sequences ofinstructions contained in memory, such as ROM 207, volatile RAM 205,non-volatile memory 206, cache 204 or a remote storage device. Invarious embodiments, hardwired circuitry may be used in combination withsoftware instructions to implement the present invention. Thus, thetechniques are not limited to any specific combination of hardwarecircuitry and software nor to any particular source for the instructionsexecuted by the data processing system. In addition, throughout thisdescription, various functions and operations are described as beingperformed by or caused by software code to simplify description.However, those skilled in the art will recognize what is meant by suchexpressions is that the functions result from execution of the code by aprocessor, such as the processor 203.

A machine readable medium can be used to store software and data, whichwhen executed by a data processing system causes the system to performvarious methods of the present invention. This executable software anddata may be stored in various places including for example ROM 207,volatile RAM 205, non-volatile memory 206 and/or cache 204 as shown inFIG. 2. Portions of this software and/or data may be stored in any oneof these storage devices.

Thus, a machine readable medium includes any mechanism that provides(i.e., stores and/or transmits) information in a form accessible by amachine (e.g., a computer, network device, personal digital assistant,manufacturing tool, any device with a set of one or more processors,etc.). For example, a machine readable medium includesrecordable/non-recordable media (e.g., read only memory (ROM); randomaccess memory (RAM); magnetic disk storage media; optical storage media;flash memory devices; etc.), as well as electrical, optical, acousticalor other forms of propagated signals (e.g., carrier waves, infraredsignals, digital signals, etc.); etc.

FIG. 3 shows a block diagram representation of a mobile stationaccording to one embodiment of the present invention. The mobile stationincludes a portable receiver, which combines a communication transceiverwith GPS receiver for use in one embodiment of the present invention.The combined mobile device 310 includes circuitry for performing thefunctions required for processing GPS signals as well as the functionsrequired for processing communication signals received through acommunication link. The communication link, such as communication link350 or 360, is typically a radio frequency communication link to anothercomponent, such as base station 352 having communication antenna 351 orwireless LAN access point 362 with antenna 361. Although FIG. 3illustrates an embodiment that communication antenna 311 is used forreceiving signals from different types of wireless access points (e.g.,from access point 362 for wireless LAN and from based station 352 forcellular phone service), the combined receiver may use separate anddistinct antennas for receiving signals of different air interfaces.Further, the combined receiver may use separate and distinct componentsfor at least a partial processing of the received wireless signals andmay or may not share some components in the processing of the wirelesssignals of different air interfaces. For example, the combined receivermay have separate circuits for the RF signal processing and share samedata processor resources. From this description, various combinationsand variations of the combined receiver will be apparent to one skilledin the art.

Mobile device 310 is an example of a combined GPS receiver and acommunication receiver and transmitter. The communication receiver andtransmitter may be implemented as multiple receivers and transmittersfor the different wireless networks. For example, the communicationtransceiver 305 may include a transceiver portion for receiving and/ortransmitting cellular telephone signals and another transceiver portionfor receiving and/or transmitting Wi-Fi signals. Mobile device 310contains a GPS receiver stage including GPS acquisition and trackingcircuit 321 and communication transceiver 305. GPS acquisition andtracking circuit 321 is coupled to GPS antenna 301, and communicationtransceiver 305 is coupled to communication antenna 311. GPS signals(e.g., signal 370 transmitted from satellite 303) are received throughGPS antenna 301 and input to GPS acquisition and tracking circuit 321which acquires the PN (pseudorandom noise) codes for the variousreceived satellites. The data produced by GPS acquisition and trackingcircuit 321 (e.g., correlation indicators) are processed by processor333 for transmittal (e.g., of SPS pseudoranges) by communicationtransceiver 305. Communication transceiver 305 contains atransmit/receive switch 331 which routes communication signals(typically RF) to and from communication antenna 311 and communicationtransceiver 305. In some systems, a band splitting filter or “duplexer,”is used instead of the T/R switch. Received communication signals areinput to communication receiver 332 and passed to processor 333 forprocessing. Communication signals to be transmitted from processor 333are propagated to modulator 334 and a frequency converter (IF/RFconverter 335). Power amplifier 336 increases the gain of the signal toan appropriate level for transmission to base station 352 (or towireless LAN access point 362).

In one embodiment of the present invention, communication transceiver305 is capable of being used with a number of different air interfaces(e.g., IEEE 802.11, bluetooth, UWB, TD-SCDMA, iDEN, HDR, TDMA, GSM,CDMA, W-CDMA, UMTS or other similar networks) for communication (e.g.,through communication links 350 and 360). In one embodiment of thepresent invention, communication transceiver 305 is capable of beingused with one air interface for communication and capable of being usedto receive signals with other air interfaces. In one embodiment of thepresent invention, communication transceiver 305 is capable of beingused with one air interface for communication while also being capableof being used with signals in another air interface to extract timingindicators (e.g., timing frames or system time) or to calibrate thelocal oscillator (not shown in FIG. 3) of the mobile station. Moredetails about the mobile station for extracting timing indicators orcalibrating the local oscillator can be found in U.S. Pat. Nos.5,874,914 and 5,945,944.

In one embodiment of the combined GPS/communication system of mobiledevice 310, data generated by GPS acquisition and tracking circuit 321is transmitted to a server over communication link 350 to base station352 or over communication link 360 to wireless LAN access point 362. Theserver then determines the location of mobile device 310 based on thedata from the remote receiver, the time at which the data were measuredand ephemeris data received from its own GPS receiver or other sourcesof such data. The location data can then be transmitted back to areceiver 332 in mobile device 310 or to other remote locations. Moredetails about portable receivers utilizing a communication link can befound in U.S. Pat. No. 5,874,914.

In one embodiment of the present invention, the combined mobile device310 includes (or is coupled to) a data processing system (e.g., apersonal data assistant or a portable computer). The data processingsystem includes a bus that is coupled to a microprocessor and a memory(e.g., ROM, volatile RAM and/or non-volatile memory). The businterconnects various components together and also interconnects thesecomponents to a display controller and display device and to peripheraldevices such as input/output (I/O) devices, which are well known in theart. The bus may include one or more buses connected to each otherthrough various bridges, controllers and/or adapters as are well knownin the art. In one embodiment, the data processing system includescommunication ports (e.g., a USB (Universal Serial Bus) port, a port forIEEE-1394 bus connection). In one embodiment of the present invention,the mobile station stores the locations and identifications (e.g., MACaddress) of wireless access points (e.g., according to the types of thewireless access points) for extracting and enhancing the locationinformation about the wireless access points using the memory andsoftware program instructions stored in the memory. In one embodiment,the mobile station only stores the locations of the mobile station andidentifications of the wireless access points for transmission to aserver (e.g., through a communication port or a wireless communicationlink) when a communication connection is established.

FIG. 4 shows one example of a hybrid positioning system according to oneembodiment of the present invention. In FIG. 4, mobile station 407utilizes signals in the air that are transmitted from both wirelessaccess point 403 of wireless network A and wireless access point 405 ofwireless network B for position determination. In one embodiment of thepresent invention, the mobile station includes a receiver for receivingSPS signals from SPS satellites (e.g., GPS satellites, not shown in FIG.4). Timing measurements (e.g., pseudorange, round trip time, times ofarrival of signals or time differences of arrival of signals) based onthe wireless signals from one or both of wireless networks A and B (andSPS signals) may be used to determine the position of the mobilestation. It is understood that, in general, each of wireless networks Aand B includes a number of access points (e.g., cellular base stationssuch as wireless access points 403 and 405). Wireless networks A and Bmay use the same type of air interface, operated by different serviceproviders or they may operate with the same communication protocols butat different frequencies. However, wireless networks A and B may alsouse different types of air interfaces (e.g., TDMA, GSM, CDMA, WCDMA,UMTS, TD-SCDMA, iDEN, HDR, bluetooth, UWB, IEEE 802.11 or other similarnetworks), operated by the same service provider or by different serviceproviders.

In one embodiment of the present invention, the position determinationis performed at location server 411 shown in the example depicted inFIG. 4. Mobile station 407 communicates the information extracted fromthe observed SPS signals (e.g., SPS pseudorange measurements and/or arecord of an SPS message for comparison to determine a time of signalreception) and the information extracted from the observed wirelesssignals (e.g., the identification of an access point, round trip orone-way time measurements between mobile station 407 and at least one ofthe wireless access points and received signal levels) to the locationserver through one of the wireless networks, such as wireless network A(e.g., when the mobile station is a subscriber of wireless network A butnot a subscriber of wireless network B). Servers 413 and 415 maintainthe almanac data for wireless networks A and B respectively. Thisalmanac data may simply be, in one exemplary implementation, a databaselisting a latitude and longitude for each wireless access point, whichis specified by an identification information (e.g., MAC address or celltower identifier, etc.). Location server 411 uses the informationcommunicated from the mobile station and the data in the almanac servers413 and 415 to determine the position of the mobile station. Thelocation server 411 may determine the location of the mobile station ina number of different ways. It may, for example, retrieve from servers413 and 415 the locations of wireless access points 403 and 405 and usethose locations and the range measurements, which indicate a distancebetween the mobile station 407 and the points 403 and 405, and the SPSpseudorange measurements and SPS ephemeris information to calculate aposition of the mobile station 407. U.S. Pat. No. 5,999,124 provides adiscussion of how range measurements from a single wireless network andSPS pseudorange measurements may be combined to calculate a position ofa mobile station. Alternatively, the location server 411 may use onlyterrestrial range measurements (or other types of measurements such assignal strength measurements) to multiple wireless access points ofmultiple wireless networks to calculate the position if many (e.g., morethan 3) such range measurements can be made; in this case, there is noneed to obtain SPS pseudoranges or SPS ephemeris information. If SPSpseudoranges to SPS satellites are available, these pseudoranges can becombined with SPS ephemeris information, obtained either by the mobilestation or by a collection of GPS reference receivers as described inU.S. Pat. No. 6,185,427, to provide additional information in theposition calculations.

Network 401 may include local area networks, one or more intranets andthe Internet for the information exchange between the various entities.It is understood that servers 411, 413 and 415 may be implemented as asingle server program or different server programs in a single dataprocessing system or in separate data processing systems (e.g.,maintained and operated by different service providers).

In one embodiment of the present invention, different service providersoperate wireless networks A and B, which are used by the mobile stationfor position determination. A typical mobile station is a subscriberonly to one of them, and thus the mobile station is authorized to use(and to have access to) only one wireless network. However, it is oftenstill possible to at least receive signals from the wireless networkthat is not subscribed to and thus it is still possible to make rangemeasurements or signal strength measurements relative to wireless accesspoints in the wireless network that is not subscribed to. One specificexample of this situation would involve a user of a tri-mode CDMAcellular phone, which can receive PCS frequency band signals (e.g., fromthe wireless network operated by Sprint, which is a first serviceprovider) and can also receive other CDMA signals at other frequencies(such as, for example, from the wireless network operated by VerizonWireless, which is a second service provider). If the user hassubscribed only to Sprint's wireless network, then the user's phone (aform of a mobile station) is authorized to operate with Sprint'swireless network but not Verizon's wireless network. The user may usethe phone in an environment in which only one Sprint wireless accesspoint (e.g., a Sprint cellular base station) is capable of radiocommunication with the user's phone, but in this environment there arenumerous Verizon wireless access points that are within radiocommunication range of the user's phone. In this context, it is stillpossible for the phone to obtain SPS assistance data (if desired) from alocation server through Sprint's wireless network and to transmit SPSpseudoranges, obtained at the phone, to the location server. However, itwill not be possible to obtain more than one range measurement to awireless access point unless range measurements to Verizon's wirelessaccess points are obtained. With an embodiment of the invention, thephone obtains range measurements to the available Verizon wirelessaccess points, thereby providing at least a few range measurements(e.g., distances between the phone and two Verizon cellular basestations) which can be used in the position calculations that areperformed to determine the position of the phone.

The service providers maintain the almanac information on servers 413and 415 separately. Although mobile station 407 has communication accessto only one of the wireless networks, location server 411 may haveaccess to both servers 413 and 415 for base station almanac data. Afterdetermining the identities of base stations (e.g., the wireless accesspoints 403 and 405) of both wireless networks A and B, the mobilestation 407 transmits the base station identifications to locationserver 411, which uses servers 413 and 415 to retrieve the correspondingpositions of the base stations, which can be used in determining theposition of the mobile station.

Alternatively, the cooperation between the service providers to sharealmanac data is not necessary. For example, the operator of locationserver 411 maintains both almanac servers 413 and 415 (e.g., through asurvey process to obtain the almanac data or through a data harvestingprocess using mobile stations, which will be described in detail withFIGS. 6 and 7 and 10).

In one embodiment of the present invention, mobile station 407 uses bothwireless networks A and B for communicating with the location server(instead of using only one of the wireless networks for communicationpurpose). As known in the art, various types of information can beexchanged between the mobile station and the location server forposition determination. For example, location server 411 can provide themobile station 407 with Doppler frequency shift information for in-viewsatellites of the mobile station (e.g., through wireless network A); andthe mobile station can provide pseudorange measurements for SPS signals,the identification information of the base stations and associated rangemeasurements (e.g., round trip time measurements) to the location serverfor the calculation of the position of the mobile station (e.g., throughwireless network B). In one embodiment of the present invention, amobile station is capable of communicating through more than onewireless network to the location server when in the coverage area ofthese wireless networks. However, the trade-off between cost andperformance may dictate communication with the server using one of thewireless networks, while using the others only for timing measurements(or other measurements, such as received signal levels) or for aiding inmeasurement, such as obtaining time information from wirelesstransmission from an access point for time stamping measurements (e.g.,for resolving ambiguity) or locking to the accurate carrier frequency ofa wireless cellular base station for calibrating the local oscillator ofthe mobile station.

In one embodiment of the present invention, the location of the mobilestation is determined at the location server using the informationcommunicated from the mobile station and then transmitted back to themobile station. Alternatively, the position calculation can be performedat the mobile station using assistance information from the locationserver (e.g., Doppler frequency shifts for in-view satellites, positionsand coverage areas of access points, differential GPS data and/oraltitude aiding information).

FIG. 5 shows another example of a hybrid positioning system according toone embodiment of the present invention. An access point of one wirelessnetwork (e.g., cellular base station 503) is used for the communicationbetween mobile station 507 and location server 511. A method fordetermining the position of mobile station 507 may use SPS signals(e.g., from satellite 521), wireless signals from access points of thewireless network used for data communication (e.g., cellular phone basestation 503), wireless signals from access points of other wirelessnetworks (e.g., wireless access point B 505, which can be a base stationof a different wireless cellular phone network such as operated by adifferent service provider or using a different air interface) and/orwireless signals from LAN access points (e.g., access point A 509 suchas a Bluetooth access point or a Wi-Fi wireless access point).

Typically, a wireless LAN access point (or other similar low powertransmitters) has a small coverage area. When available, the smallcoverage area of such an access point provides a very good estimate ofthe location of the mobile station. Further, wireless LAN access pointsare typically located near or inside buildings, where the availabilityof other types of signals (e.g., SPS signals or wireless telephonesignals) may be low. Thus, when such wireless transmissions are usedwith other types of signals, the performance of the positioning systemcan be greatly improved.

In one embodiment of the present invention, the wireless signals fromdifferent wireless networks are used for position determination. Forexample, the wireless signals from the different wireless networks canbe used to determine the identities of the corresponding access points,which are then used to determine the locations and coverage areas of thecorresponding access points. When precision range information (e.g.,round trip time or signal traveling time between an access point and themobile station) is available, the range information and the location ofthe access point can be used in obtaining a hybrid positioning solution.When approximate range information (e.g., received signal level, whichcan be approximately correlated with an estimated range) is available,the location of the access point can be used to estimate the position ofthe mobile station (or determine the estimated altitude of the mobilestation). Further, the mobile station can use precision carrierfrequency from one of the wireless networks (e.g., from access point 505or 509), which may not be the one used for the data communicationpurpose, to calibrate the local oscillator of the mobile station. Moredetails about locking to a precision carrier frequency of a wirelesssignal to provide a reference signal at an SPS receiver for signalacquisition can be found in U.S. Pat. No. 5,874,914. Further, the mobilestation can use the accurate time information in the wireless signalsfrom one of the wireless networks (e.g., from access point 505 or 509),which may not be the one used for the data communication purpose. Moredetails about using the accurate time information (e.g., timing markersor system time) for time stamping can be found in U.S. Pat. No.5,945,944.

Since some of the access points of the different wireless networks donot have well-known almanac data (e.g., position of the wireless accesspoint and/or coverage area of the wireless access point), one embodimentof the present invention derives the almanac data from the informationcollected from mobile stations. FIG. 6 illustrates one method todetermine the position of a wireless access point according to oneembodiment of the present invention. In FIG. 6, a location server doesnot know the position of access point antenna 601. To calculate theposition of the access point, the location server correlates thepositions of one or more mobile stations and their corresponding rangesto the access point, which are obtained from the mobile stations whileperforming position determination for the mobile stations. For example,a mobile station at position L₁ 611 determines range R₁ 613 to accesspoint antenna 601. The mobile station obtains measurements based on SPSsignals (e.g., measurements of SPS pseudoranges and extraction of SPSephemeris information from SPS signals) and wireless transmissions(e.g., range measurements). The mobile station may calculate itsposition using the measurements and transmit to the location server thecalculated position with: i) the range to the access point antenna; andii) the identity of the access point antenna. Alternatively, the mobilestation may transmit: i) the measurements; ii) the range to the accesspoint antenna; and iii) the identity of the access point antenna to thelocation server, which calculates the position of the mobile stationusing the measurements and which stores the range measurements (e.g.,R₁, R₂ and R₃ and the corresponding positions (e.g., L₁, L₂ and L₃).When a number of data points are available, each of which data pointscorrelates the position of a mobile station and the range from themobile station to the access point antenna, the location serverdetermines the position of the access point antenna. It can be seen fromFIG. 6 that as few as three range measurements (R₁, R₂ and R₃) and theircorresponding positions (L₁, L₂ and L₃) are sufficient to specify aparticular location of the identified access point (which is shown atthe intersection of three circles specified by the three ranges).Various methods that have been used in the art for calculating theposition of a mobile station based on range information can be used tocalculate the position of the access point. Note that the data pointsmay be from a single mobile station or from a number of mobile stations.

Further, the accumulated data points of the locations of mobile stationsshow the coverage area of the access point (e.g., in a scatter plot ofthe mobile locations). When the position of the access point is notknown, the collected data points can be used to estimate the positionand the coverage of the access point. When an initial estimation of theposition of the access point is available, the collected data points canbe used to improve the estimation. The collection and enhancementprocess can be a continuous process during the service of the locationserver. Note that the collection and enhancement operations can also beperformed on a different server other than the location server. Forexample, in one embodiment of the present invention, the collection andenhancement operations are performed in almanac server 513, whichcommunicates with location server 511 in performing hybrid positiondetermination for mobile stations.

However, precision information of range to some access points may not beavailable to mobile stations of a location server 511. FIG. 7illustrates another method to determine the position information of awireless access point according to one embodiment of the presentinvention. A larger number of data points (e.g., 711, 713, 715, 721,723, 725) of the locations of mobile stations that can receive signalsfrom the access point (e.g., 703) define a coverage area (e.g., 705) ofthe access point (e.g., through a scatter plot of the locations or thesmallest circle enclosing the data points). From the coverage area, thelocation server can calculate an estimated position of the access point(e.g., the geometric center of the coverage area). Further, rangeinformation (e.g., an indicator of the received signal level and/or around trip time) may be used to define a weight for determining theweighted average of the coverage area (e.g., the closer to the accesspoint, the larger the weight), from which the estimated position of theaccess point is determined. Further, in one embodiment, the locationserver determines the probability of a mobile station being at aparticular location from the statistics of the mobile stations, givencertain range information is specified. Other information, such as thesignal level of wireless transmission from other transmitters, can thenbe further used to narrow the possible locations of the mobile station.

For example, a wireless LAN access point is located inside building 701.While SPS signals (e.g., signals from SPS satellites 741-745) andwireless cellular phone signals (e.g., signals from cellular basestation 751) may be weak inside building 701, the position of a mobilestation can be easily determined (e.g., without using the signals fromaccess point 703) at certain locations around the building (e.g.,locations 711-725, which may be just outside the building or at certainlocations inside the building, such as spots close to windows). In oneembodiment of the present invention, the identification of the accesspoint is determined and sent to the server with the location of themobile station (or information specifying the location of the mobile,such as pseudoranges to in-view satellites) for the determination of thecoverage area (and/or the position) of the access point 703. Thelocation information of the access point (e.g., coverage area and/orposition) can be maintained at the server (or a different server). Whena mobile station is inside a building (or at a position near thebuilding), where the blockage of some of the SPS signals and cellularphone signals occurs, the location information about the access pointcan be used to aid in determining the position of the mobile station.

It is understood that some access points may be moved from one locationto another. In one embodiment of the present invention, the servertracks the collected position information about one or more mobilestations that receive the transmission from one access point in order todetermine if the access point is moved. For example, the server maycompare the old coverage area with the recent coverage area (e.g.,through comparing the center and the radius of the coverage area) todetermine if the access point is moved. Alternatively, the server mayperiodically discard old information in view of newly collectedinformation. Further, the server may weight the collected information sothat the freshly collected data carries more weight in determining thecoverage area and/or the location of the access point and the influencefrom the data collected previously may eventually diminish over time.Further, the server may determine if an access point moves frequently;and, if the access point moves frequently, the access point may bedisqualified as a reference point for the position determination.Further, in one embodiment, when an access point has not been observedfor a certain period of time, the access point is removed from thedatabase; similarly, when a new access point is observed, it is added tothe database. Thus, the server may update the information about theaccess point in an ongoing basis.

In at least one embodiment of the present invention, a mobile stationcan determine its position without a communication link. The mobilestation has memory for storing at least some of the information aboutthe locations of the mobile station and the corresponding receivedsignal levels or range measurements of a number of wireless accesspoints (e.g., for cellular phone access or for wireless LAN access). Themobile station transmits the data to a server when a communication link(e.g., a wire connection through a communication port of the mobilestation or a wireless connection through a transceiver of the mobilestation) is available. Alternatively, the mobile station may directlyuse the stored information to derive the position information about theaccess point in determining its own position when needed.

FIG. 8 shows a general method of hybrid position determination using aplurality of wireless networks according to one embodiment of thepresent invention. In operation 801, a mobile station receives wirelesssignals transmitted from a plurality of wireless access points ofdifferent wireless networks (e.g., wireless networks of different airinterfaces, wireless networks of different service providers, wirelessnetworks operating at different frequencies, wireless networks usingdifferent communication protocols, etc.). In operation 803, the mobilestation utilizes the wireless signals from each of the access points ofthe different wireless networks in determining the position of themobile station (e.g., to determine the identity of the access point, tolock a local oscillator of the mobile station to a precision carrierfrequency of a wireless signal, to obtain a timing indicator from awireless signal, to determine signal transmission delay between themobile station and one of the access points and/or to communicate with aserver). In general, the mobile station may use the wireless signalsfrom access points of different wireless networks to perform differentoperations, although the mobile station may use the wireless signalsfrom access points of some different wireless networks to perform anumber of similar operations. In operation 805, the mobile stationcommunicates with a server to determine the position of the mobilestation using at least one of the different wireless networks.Typically, the mobile station communicates with the server using onlyone of the different wireless networks; however, the mobile station maycommunicate with the server using more than one wireless network (e.g.,to transmit the time of reception at an access point for a signaltransmitted from the mobile station, to transmit a round trip time or totransmit other information to or from a location server).

FIG. 9 shows a method of hybrid position determination using twowireless networks for communication with a server according to oneembodiment of the present invention. Operation 821 receives, at a mobilestation, SPS signals transmitted from one or more SPS satellites andwireless signals transmitted from a plurality of wireless access pointsof more than one wireless network. The mobile station may use thereceived wireless signals from one or more wireless networks to aid inSPS signal acquisitions (e.g., to extract Doppler frequency shifts forin-view satellites of the mobile station, to calibrate the localoscillator of the mobile station and/or to obtain a timing indicator totime stamp a measurement). The mobile station uses the SPS signals todetermine pseudoranges to in-view satellites and wireless signals fromthe wireless access points to identify the access points and to performrange measurements to the wireless access points for positiondetermination. These received signals are typically broadcast from thetransmitters of the satellites and wireless access points and availableto any mobile station that chooses to use them. Operation 823communicates first information (e.g., a record of an SPS message)between the mobile station and a server using an access point of a firstwireless network (e.g., a wireless local area network). Operation 825communicates second information (e.g., Doppler frequency shifts,ephemeris data for in-view SPS satellites) between the mobile stationand a server using an access point of a second wireless network (e.g., awireless cellular phone network). Operation 827 determines the positionof the mobile station from the communication of the first informationand the second information. Typically, the availability, coverage,expense, data speed and ease of use are considered when choosing whichcommunications path to use. Further, the mobile station may usedifferent communication paths at different locations. For example, whenthe mobile station is within the coverage area of a wireless LAN (e.g.,a home network), the mobile station may use the wireless LAN (e.g.,through the internet) to communicate with the server for informationthat does not need to pass through the base station of a wirelesscellular phone system (e.g., Doppler frequency shifts); and use the basestation of the wireless cellular phone system to transmit theinformation that is related to the base station (e.g., round trip timemeasurement to the base stations of the wireless cellular phone system).In a further example, the mobile station may choose to use either thewireless cellular phone system or the wireless LAN for communicationaccording to the communication cost and availability. In one embodimentof the present invention, the mobile station automatically determinesthe communication path according to a set of rules (e.g., availability,cost, priority and others) which may be specified by a user of themobile station or may be set as a default setting by one of the wirelessnetworks.

FIG. 10 shows a method to generate location information about a wirelessaccess point according to one embodiment of the present invention.Operation 841 detects, at a mobile station, wireless signals transmittedfrom a wireless access point (e.g., a wireless access point that is incompliance with the IEEE 802.11 standard for wireless local area networkor other types of ground-based wireless transmitters that transmitsignals with their identification information). Note that, in thepresent application, wireless access points do not includesatellite-based transmitters. Operation 843 determines identificationinformation, which may be a unique identifier, of the wireless accesspoint (e.g., the MAC address of the wireless access point or anidentifier of a cellular base station) from the wireless signals.Operation 845 determines the position of the mobile station (e.g., atthe mobile station or at a location server). For example, the mobilestation may calculate the position based on the pseudorange measurementsand other range information; or, the mobile station may transmit thepseudorange measurements and the range information to a location server,which calculates the position of the mobile station (and the locationserver may send back the calculated position to the mobile station).Operation 847 correlates the position of the mobile station with theidentification information of the wireless access point. Thiscorrelation may be transmitted to a location server so that futurepositioning operations of mobile stations may use the position andidentification information to determine a position of the identifiedwireless access point. Operation 849 generates location informationabout the wireless access point (e.g., access point almanac, statisticsof coverage area of the wireless access point). Typically, thecorrelation data is sent to a server (e.g., a location server or anaccess point almanac server) which generates location information aboutthe access point based on a number of positions of one or more mobilestations that report the reception of signals transmitted from theaccess point. The location information about the wireless access pointcan be derived from a weighted average method as described above (orother methods, such as, using the range information as shown in FIG. 6).However, a mobile station may also track the correlation and derive thelocation information about the wireless access point (e.g., from datapoints collected at different time instances). The location informationabout the wireless access point can then be used for positiondetermination.

FIG. 11 shows a hybrid position determination method using one wirelessnetwork for communication and another wireless network for themeasurement of positioning parameters according to one embodiment of thepresent invention. Operation 861 detects, at a mobile station, wirelesssignals transmitted from a wireless access point (e.g., a wirelessaccess point that is in compliance with the IEEE 802.11 standard forwireless local area network or a cellular communication base station) ofa first wireless network (e.g., a wireless local area network or acellular phone communication system). Operation 863 determines theidentification information of the wireless access point (e.g., the MACaddress or the base station ID) from the wireless signals. Operation 865retrieves location information about the wireless access point (e.g.,access point almanac) using the identification information. For example,the mobile station may transmit identification information of thewireless access point to location server, which retrieves the locationinformation about the wireless access point using the identificationinformation (e.g., from a database or from another server, such as anaccess point almanac server). In another example, the mobile stationmaintains the location information about the wireless access point inmemory; thus, the location information is simply retrieved from thememory of the mobile station. Operation 867 determines the position ofthe mobile station using the location information and using acommunication link between the mobile station and a wireless accesspoint of a second wireless network (e.g., a cellular phone network). Forexample, satellite assistance data (e.g., Doppler frequency shifts) forthe acquisition of SPS signals or timing measurements (e.g.,pseudoranges or time of arrivals of SPS signals) are communicatedthrough the second wireless network for the determination of theposition of the mobile station.

FIG. 12 shows another exemplary method of the inventions. In thismethod, a mobile station receives, in operation 901, first signalstransmitted from a first wireless access point of a first wirelessnetwork. The first wireless network may support two way communicationbetween the various nodes within the first wireless network as well asnodes outside of this network. In operation 903, at least one rangemeasurement is determined using the first signals. If additional signalsfrom other wireless access points of the first wireless network are alsoavailable, then additional range measurements to these other wirelessaccess points (and their identification information) are obtained. In analternative implementation of operation 903, another measurement (e.g.,a signal strength measurement of the first signals) may be taken by themobile station without attempting to make a range measurement using thefirst signals. In one exemplary implementation, a time of travel of thefirst signals from the first wireless access point to the mobile stationis measured and an identification of this first wireless access point isreceived from the first wireless access point. In operation 905, secondsignals are communicated between the mobile station and a secondwireless access point of a second wireless network, which is differentthan the first wireless network. The mobile station may, in thisoperation, receive the second signals (which may include SPS assistancedata, etc.) from the second wireless access point. In operation 907, themobile station and the server communicate to determine the position ofthe mobile station. This communication may be through the secondwireless access point. For example in operation 907, the mobile stationmay transmit the range measurements and identification information (fromoperation 903) and SPS pseudoranges (obtained by the mobile station) tothe server through the second wireless access point. The identificationinformation is used to obtain the location of the wireless access pointsto which range measurements (or other measurements) were obtained andthe server may then determine the position of the mobile station usingat least some of the available measurements (e.g., the SPS pseudorangesto SPS satellites and the range measurements or other measurements, tovarious terrestrial wireless access points). Alternatively, the mobilestation may determine its position (rather than the server doing so)using the range measurements and SPS pseudoranges and using informationprovided by the server (such as the location of the identified wirelessaccess points in one or both of the wireless networks).

The first wireless network in FIG. 12 may be a wireless local areanetwork and, in this case, the first wireless access point may be awireless router operating according to a Wi-Fi standard. Alternatively,the first wireless network may be a wireless cellular telephone networkoperated by a first service provider and the second wireless network maybe another (different) wireless cellular telephone network operated by asecond service provider. The mobile station, which may be a cellulartelephone with an integrated GPS receiver, is authorized to operate withonly the second wireless network and not the first wireless network.Various other alternatives, discussed herein, may also apply to thisexample of FIG. 12.

FIG. 13 is another example of a method of the inventions. In thisexample, the mobile station, in operation 931, obtains an identificationinformation of a first wireless access point of a first wireless networkthat is accessible (e.g., within radio communication) to the mobilestation. This identification may be a MAC address (e.g., in an Ethernetlocal area network) or a cellular telephone base station (e.g., “celltower”) identifier. In operation 933, the mobile station transmits,through a second wireless access point of a second wireless network, theidentification information to a server (e.g., a location server) duringa position determination operation. In this example, the second wirelessnetwork is different than the first wireless network (e.g., differentair interfaces, different service providers, etc.). Then, in operation935, the server uses the identification information of the firstwireless access point to determine the location of the first wirelessaccess point (which may have been harvested/collected through methodsdescribed herein, such as in FIG. 14). The server may also, in operation935, use other data (e.g., SPS pseudoranges determined at a GPS receiverthat is integrated into the mobile station and then transmitted to theserver) to determine the position of the mobile station. The server may,for example, combine the SPS pseudoranges with the measurements onsignals from the wireless access points to determine the position of themobile station. Alternatively, the SPS pseudoranges may be combined withthe known locations of the wireless access points (particularly in thecase of wireless LANs, which have shorter signal ranges). In anotheralternative to operation 935, the server may provide assistance data(e.g., the location of the first wireless access point and possiblyother data such as Doppler data for SPS satellites in view of the mobilestation, etc.) to the mobile station but the server does not compute theposition of the mobile station; rather, the mobile station performs theposition solution using at least some of the available measurements(e.g., SPS pseudoranges, range measurements or other measurementsrelative to the wireless access points of one or all available wirelessnetworks) and the available assistance data from the server.

FIG. 14 shows another exemplary method of the inventions. This methodultimately determines positions of wireless access points so that futureposition determination operations for mobile stations can be performedusing multiple wireless networks as described herein. In operation 971,data is collected. This data specifies a plurality of locations ofmobile stations at which wireless signals, transmitted from at least afirst wireless access point of a first wireless network, are receivedduring determinations of the plurality of locations. The mobile stationsmay, in operation 973, receive signals from the first wireless accesspoints and also communicate signals between the mobile stations and atleast one second wireless access point of a second wireless network(which is different than the first wireless network). This communicationwith the second wireless network may be for the purpose of providinginformation used in collecting the data, which is used to determine thelocations of wireless access points of the first wireless network. Inoperation 975, the location of at least the first wireless access pointis determined (e.g., in the manner shown in FIG. 6) from the coveragearea defined by the plurality of locations.

Although the methods and apparatus of the present invention have beendescribed with reference to GPS satellites, it will be appreciated thatthe descriptions are equally applicable to positioning systems, whichutilize pseudolites or a combination of satellites and pseudolites.Pseudolites are ground-based transmitters, which broadcast a PN code(similar to a GPS signal), typically modulated on an L-band carriersignal, generally synchronized with GPS time. Each transmitter may beassigned a unique PN code so as to permit identification by a remotereceiver. Pseudolites are useful in situations where GPS signals from anorbiting satellite might be unavailable, such as tunnels, mines,buildings or other enclosed areas. As used herein, the term “satellite”is intended to include pseudolites or equivalents of pseudolites and theterm GPS signals is intended to include GPS-like signals frompseudolites or equivalents of pseudolites.

In the preceding discussion the invention has been described withreference to application upon the United States Global PositioningSatellite (GPS) system. It should be evident, however, that thesemethods are equally applicable to similar satellite positioning systems,and in particular, the Russian GLONASS system and the proposed EuropeanGalileo System. The GLONASS system primarily differs from GPS system inthat the emissions from different satellites are differentiated from oneanother by utilizing slightly different carrier frequencies, rather thanutilizing different pseudorandom codes. In this situation substantiallyall the circuitry and algorithms described previously are applicable.The term “GPS” used herein includes such alternative satellitepositioning systems, including the Russian GLONASS system and theEuropean Galileo System.

Although the operations in the above examples are illustrated inspecific sequences, from this description, it will be appreciated thatvarious different operation sequences and variations can be used withouthaving to be limited to the above illustrated examples.

The above examples are illustrated without presenting some of thedetails known in the art; as pointed out in the above discussion, thesedetails can be found in publications, such as U.S. Pat. Nos. 5,812,087,5,841,396, 5,874,914, 5,945,944, 5,999,124, 6,061,018, 6,208,290 and6,215,442, all of which are hereby incorporated here by reference.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

What is claimed is:
 1. A method of determining a position of a mobilestation, the method comprising: receiving wireless signals from a firstwireless network; receiving wireless signals from a second wirelessnetwork; determining signal strength of the wireless signals from thefirst wireless network and the wireless signals from the second wirelessnetwork; and determining the position of the mobile station based atleast in part on the signal strength.
 2. The method of claim 1, themethod further comprising: receiving, at a receiver, SatellitePositioning System (SPS) signals from SPS satellites; wherein the act ofdetermining the signal strength is further based on the SPS signals fromthe SPS satellites.
 3. The method of claim 1, wherein the first wirelessnetwork and the second wireless network use a common air interfacestandard.
 4. The method of claim 1, wherein the first wireless networkand the second wireless network are operated by different serviceproviders.
 5. The method of claim 1, wherein the first wireless networkand the second wireless network operate with a common communicationprotocol.
 6. The method of claim 1, wherein the first wireless networkand the second wireless network operate with one or more commoncommunication protocol.
 7. The method of claim 1, wherein the firstwireless network and the second wireless network operate differentcommunication protocols and are operated by a common service provider.8. The method of claim 1, wherein the act of determining the position ofthe mobile station based on the signal strength occurs at a locationserver.
 9. The method of claim 1, wherein the mobile station is notsubscribed to the first wireless network, and wherein the mobile stationis subscribed to the second wireless network.
 10. The method of claim 9,further comprising: obtaining assistance data from the first wirelessnetwork.
 11. The method of claim 10, wherein the assistance datacomprises Satellite Positioning System (SPS) assistance data.
 12. Themethod of claim 10, further comprising: obtaining assistance data fromthe first wireless network; and transmitting pseudorange measurements toa location server.
 13. An apparatus for determining a position of themobile station, the mobile device comprising: means for receivingwireless signals from a first wireless network; means for receivingwireless signals from a second wireless network; means for determiningsignal strength of the wireless signals from the first wireless networkand the wireless signals from the second wireless network; and means fordetermining the position of the mobile station based at least in part onthe signal strength.
 14. The apparatus of claim 13, further comprising:means for receiving Satellite Positioning System (SPS) signals from SPSsatellites, wherein the means for determining the signal strength usesthe SPS signals from the SPS satellites.
 15. The apparatus of claim 13,wherein the first wireless network and the second wireless network use acommon air interface standard.
 16. The apparatus of claim 13, whereinthe first wireless network and the second wireless network are operatedby different service providers.
 17. The apparatus of claim 13, whereinthe first wireless network and the second wireless network operate witha common communication protocol.
 18. The apparatus of claim 13, whereinthe first wireless network and the second wireless network operatedifferent communication protocols and are operated by a common serviceprovider.
 19. The apparatus of claim 13, wherein the means fordetermining the position of the mobile station based on the signalstrength comprises a location server.
 20. The apparatus of claim 13,wherein the mobile station is not subscribed to the first wirelessnetwork, and wherein the mobile station is subscribed to the secondwireless network.
 21. The apparatus of claim 20, further comprising:means for obtaining assistance data from the first wireless network. 22.The apparatus of claim 21, wherein the assistance data comprisesSatellite Positioning System (SPS) assistance data.
 23. The apparatus ofclaim 21, further comprising: means for obtaining assistance data fromthe first wireless network; and means for transmitting pseudorangemeasurements to a location server.
 24. A mobile device comprising aprocessor and a memory wherein the memory includes software instructionsconfigured to cause the mobile device to: receive wireless signals froma first wireless network; receive wireless signals from a secondwireless network; determine signal strength of the wireless signals fromthe first wireless network and the wireless signals from the secondwireless network; and determine the position of the mobile station basedat least in part on the signal strength.
 25. The mobile device of claim24, wherein software instructions are further configured to cause themobile device to: receive Satellite Positioning System (SPS) signalsfrom SPS satellites, wherein the act of determining the signal strengthis further based on the SPS signals from the SPS satellites.
 26. Themobile device of claim 24, wherein the first wireless network and thesecond wireless network use a common air interface standard.
 27. Themobile device of claim 24, wherein the first wireless network and thesecond wireless network are operated by different service providers. 28.The mobile device of claim 24, wherein the first wireless network andthe second wireless network operate with a common communicationprotocol.
 29. The mobile device of claim 24, wherein the first wirelessnetwork and the second wireless network operate with one or more commoncommunication protocol.
 30. The mobile device of claim 24, wherein thefirst wireless network and the second wireless network operate differentcommunication protocols and are operated by a common service provider.31. The mobile device of claim 24, wherein the mobile station is notsubscribed to the first wireless network, and wherein the mobile stationis subscribed to the second wireless network.
 32. The mobile device ofclaim 31, wherein software instructions are further configured to causethe mobile device to: obtain assistance data from the first wirelessnetwork.
 33. The mobile device of claim 32, wherein the assistance datacomprises Satellite Positioning System (SPS) assistance data.
 34. Themobile device of claim 32, wherein software instructions are furtherconfigured to cause the mobile device to: obtain assistance data fromthe first wireless network; and transmit pseudorange measurements to alocation server.
 35. A non-transitory computer-readable medium tangiblyembodying a program of machine-readable instructions executable by adigital processing apparatus to perform a method for determining aposition of a mobile station having memory and a processor, said methodcomprising operations of: receiving wireless signals from a firstwireless network; receiving wireless signals from a second wirelessnetwork; determining signal strength of the wireless signals from thefirst wireless network and the wireless signals from the second wirelessnetwork; and determining the position of the mobile station based atleast in part on the signal strength.
 36. The non-transitorycomputer-readable medium of claim 35, said method further comprisingoperations of: receiving, at a receiver, Satellite Positioning System(SPS) signals from SPS satellites, wherein the act of determining thesignal strength is further based on the SPS signals from the SPSsatellites.
 37. The non-transitory computer-readable medium of claim 35,wherein the first wireless network and the second wireless network use acommon air interface standard.
 38. The non-transitory computer-readablemedium of claim 35, wherein the first wireless network and the secondwireless network are operated by different service providers.
 39. Thenon-transitory computer-readable medium of claim 35, wherein the firstwireless network and the second wireless network operate with a commoncommunication protocol.
 40. The non-transitory computer-readable mediumof claim 35, wherein the first wireless network and the second wirelessnetwork operate with one or more common communication protocol.
 41. Thenon-transitory computer-readable medium of claim 35, wherein the firstwireless network and the second wireless network operate differentcommunication protocols and are operated by a common service provider.42. The non-transitory computer-readable medium of claim 35, wherein theact of determining the position of the mobile station based on thesignal strength occurs at a location server.
 43. The non-transitorycomputer-readable medium of claim 35, wherein the mobile station is notsubscribed to the first wireless network, and wherein the mobile stationis subscribed to the second wireless network.
 44. The non-transitorycomputer-readable medium of claim 43, said method further comprisingoperation of: obtaining assistance data from the first wireless network.45. The non-transitory computer-readable medium of claim 44, wherein theassistance data comprises Satellite Positioning System (SPS) assistancedata.
 46. The non-transitory computer-readable medium of claim 44, saidmethod further comprising operations of: obtaining assistance data fromthe first wireless network; and transmitting pseudorange measurements toa location server.
 47. A method of determining a position of a mobilestation, the method comprising: receiving wireless signals from a firstbase station in a first wireless network; receiving wireless signalsfrom a second base station in a second wireless network; determining afirst identity of the first base station in the first wireless network;determining a second identity of the second base station in the secondwireless network; determining which of the two networks through which tocommunicate with a location server having access to a base stationalmanac based upon a communication subscription or connection status;transmitting the first and second base station identities to thelocation server via the determined network; receiving, from the locationserver, corresponding positions of the first and second base stations;and determining the position of the mobile station based on the receivedpositions.
 48. A mobile device for determining a position of the mobilestation, the mobile device comprising: means for receiving wirelesssignals from a first base station in a first wireless network; means forreceiving wireless signals from a second base station in a secondwireless network; means for determining a first identity of the firstbase station in the first wireless network; means for determining asecond identity of the second base station in the second wirelessnetwork; means for determining which of the two networks through whichto communicate with a location server having access to a base stationalmanac based upon a communication subscription or connection status;means for transmitting the first and second base station identities tothe location server via the determined network; means for receiving,from the location server, corresponding positions of the first andsecond base stations; and means for determining the position of themobile station based on the received positions.
 49. A mobile devicecomprising a processor and a memory wherein the memory includes softwareinstructions to: receive wireless signals from a first base station in afirst wireless network; receive wireless signals from a second basestation in a second wireless network; determine a first identity of thefirst base station in the first wireless network; determine a secondidentity of the second base station in the second wireless network;determine which of the two networks through which to communicate with alocation server having access to a base station almanac based upon acommunication subscription or connection status; transmit the first andsecond base station identities to the location server via the determinednetwork; receive, from the location server, corresponding positions ofthe first and second base stations; and determine the position of themobile station based on the received positions.
 50. A non-transitorycomputer-readable medium tangibly embodying a program ofmachine-readable instructions executable by a digital processingapparatus to perform a method for determining a position of a mobilestation having memory and a processor, said method comprising operationsof: receiving wireless signals from a first base station in a firstwireless network; receiving wireless signals from a second base stationin a second wireless network; determining a first identity of the firstbase station in the first wireless network; determining a secondidentity of the second base station in the second wireless network;determining which of the two networks through which to communicate witha location server having access to a base station almanac based upon acommunication subscription or connection status; transmitting the firstand second base station identities to the location server via thedetermined network; receiving, from the location server, correspondingpositions of the first and second base stations; and determining theposition of the mobile station based on the received positions.
 51. Themethod of claim 1, wherein determining the position of the mobilestation is further based on signal strengths of wireless signalsreceived from third and fourth wireless networks.
 52. The method ofclaim 47, wherein determining which of the two networks through which tocommunicate with the location server comprises selecting both the firstnetwork and the second network for communicating with the locationserver.
 53. The method of claim 47, wherein determining which of the twonetworks through which to communicate with the location server comprisescalculating a trade-off between cost and performance of using the firstnetwork as compared to the second network for communicating with thelocation server.